Electric-motor control



Nov. 25, 1924- H. C. HASTINGS ET AL MOTOR CONTROL ELECTRIC Filed-Hatch 10. 1923 2 Shoots-Shoot 1 Inventor-s Hammond C. Hastings, Charles T. Hanna,

Their Attorney.

Nov. 25, 1924- 1,517,233

- H. C. HASTINGS ET AL ELECTRI C MOTOR CONTROL Filod llarch 1O 1923 2 Shasta-Shoot 2- InVentor-s'. Hammond C. Hastings,

Charles T Hanna,

Their Attorney.

Patented Nov. 25, 1924.

UNITED STATES PATENT OFFICE.

CH ARLES HASTINGS AND CHARLES THOMAS HANNA, OF RUGBY, ENG- YORK.

LAND, ABSIONOBS TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW ELECTRIC-MOTOR common.

Application filed larch 1.0, 1923. Serial No. 624,226.

To all whom it may convent:

Be-it known that we, HAMMOND CHARLES HASTINGS and CHARLEs THOMAS HANNA, Subjects of the King of Great Britain, resid ing at Rugby, England, have invented certam new and useful Improvements in Electric-Motor Controls, of which the fol-' lowing is a specification.

The invention relates to the control of electric motors and has for its object to provide an improved method of and apparatus for their control so as to obtain very slow speeds at all loads. The invention is partlcularly a plicable for controlling series motors use -for operating foundry cranes,

for example, where very slow speeds are desirable for lifting patterns from the moulds, but it is also apphcable to shunt and compound wound motors, and may be used for any other purpose where slow speeds are desired. a I

The method neralladopted for obtaining slow spee s at al loads with a series motor consists in diverting or shunting from the armature of the motor a part of the current flowing through the series field wind ing and for this purpose the controller is provided with a few control points next to the off position arranged to shunt from the armature throu a resistance a portion of the series fiel current. For higher speeds the shunt circuit round the armature is opened and control is effected by varying the series resistance only.

This combination gives satisfactory control of speed, but if, when the motor is running at a high speed, the controller handle is moved back from the series control notches through the slow motion points to the off position, excessive currents may be generated on the slow motion points, causing had arcing at the commutator of the motor and also destructive arcing in the control device. The braking currents generated in this system of control may also subject the motor and stresses.

The object 'of this invention is to overcome this trouble, and to that end it consists in providing means for insuring that the gears to severe mechanical shunt circuit round the armature cannot be closed when the controller is being returned from the high speed running points to the off position. I a

In carrying the invention into effect in one form, we provide a controller having two cylinders operated by separate handles, one cylinder being used for regulating the resistance in the shunt circuit andthe other being used in conjunction with the first for slow speed control, but adapted; to be used separately for controllin the higher speeds.

The accompanying one method of carryin this invention into effect, Figs. 1 and 2 eing diagrammatic views showing the controllers and connections and Figs. 3, 4 and 5 showing one method of interlocking the two controllers. In Fig. 1 the cylinders I and II are shown in the off position,II being the separately operable cylinder controlling the resistances R to R, which for slow speeds are connected as a shunt to the armature, as shown in Fig.2. This cylinder is-referied to hereinafter as the armature shunt cylinder.

The controller illustrated is suitable for reversing and for controlling the motor at slow and high speeds, both forward and reverse.

The two cylinders I and II are mechanically interlocked, so that the armature shunt cylinder II can be moved from the off position onl when the main cylinder I'is in the ofi' position; also when the armature shunt cylinder is in any position other than the oil v position the main cylinder can be moved only to the first .few resistance notches. Generally two oints are suflicient for giving all the contro that isnecessary, thus, whenever the shunt circuit round the armature is completed by the cylinder II the main cylinder I cannot be moved to cut out more than a limited amount of the resistance R R. This insures that the motor will run at a slow speed, the connections being as shown in Fig. 2.

The interlock between the two cylinders is also arranged so that the armature shunt cylinder cannot be moved back to its ofl position the cylinder I has been rawings illustrate previously returned to, and is in the oil position. This insures that all arcing due to opening the main circuit occurs on the contacts of the main cylinder I. It also insures'that excessive braking currents cannot be generated when returning the main cylinder handle'quickly point to the ofl position.

. This willbe clearly seen when it is observed that the highspeed control points can be obtained only by moving the main cylinder I past the second notch,"'an'd"this cannot be done unless the armature shunt circuit is opened. Whe'n'the main cylinder is returned from the high speed points to the off position no armature shunt circuits are made which would cause the braking currents to be generated;'

One method or interlocking the two cylinders in order to obtain the conditions described above can be carried out as shown in'Fi 3,14 and 5. 1 p I lie erring to Fig. 3, the armature shunt cylinder and B the series control from the high speed cylinder. The figuresho ws both cylinders in the off position. Assuming ordinary series controlisrequired, cylinder B can be moved in "either direction, but before reaching the first oint in either direction, the'cam J moves 'e lever C pivoted at P over to the left "(see Fig. 4), and locks cylinder'A in the oil? "osition; I

On returning cylin or B to the 01? position the spring E pullsflever G into the original 4 ssuming'armature shunt, or slow motion control. is required, cylinder A is first moved to position 1, 2, 3 or 4 (depending on the speed required) This is shown in Fig. 5 and xepresentscylinder A moved over to a position corresponding to the first notch. The movement of this cylinder engages cam N 0 r0ller F and operates lever D, pivoted on G, so that the front end of this lever is de ressed in order to engage on projection corresponding to the second notch on gylinder B. Having set cylinder A to a re etermined notch, cylinder B can then e rotated in either direction to either notch 1 or notch 2. The movement of this cylinder moves lever C over to the left as before and locks cylinder A against return to the oil position by means of projection K engagin against lever C It is therefore impossib e to open the armature shunt circuit except when cylinder B is in the off position.

On cylinder A a projection M acts as a stop when it engages lever C corresponding to the fourth notch, preventing further movement of c linder A I When cylin er A. is returned to the off position, spring E pulls lever Ddown and disengages lever D from projection H.

It will be observed that while we have positionandrelea ses cylinder A.

referred to. the switch mechanism for establishing the shunt path about the motor armature as a cylinder, any other suitable switch or switch mechanism may be used to establish this shunt circuit.

In accordance with the provisions of the patent statutes, we have described the prin ciple of operation of our invention, together with the apparatus which we now. consider to represent the best embodiment thereof; but we desire to have it understood that the apparatus shown is only illustrative, and that the invention can be carried out by other means.

What we claim as new and desire to secure by Letters Patent of the United States, is,-

lrMeans for controlling a variable resistor in series with the armature of an electric motor and for controlling a shunt circuit to the motor armature comprising a cylinder having an oil and a plurali. of operative positions for controlling the said series resistor, separately operable switch mechanism for controlling the said shunt to the motor armature, and interlocking connections between the said cylinder and the said switch mechanism for preventing establishing the shunt about the motor armature unless the said cylinder is in the off position and for then preventing short circuiting the entire series resistor by the said cylinder with the armature shunt established by the said switch mechanism.

2. Means for controlling a variable resistor in series with the armature of an electric motor and for controlling a. shunt circuit to the motor armature comprising a cylinder havin an oil and a plurality of operative positions for controlling the said series resistor, separately operable switch mechanism for controlling the said shunt to the motor armature, and interlocking connections between the said cylinder and the said switch mechanism for preventing establishing a shunt about the motor armature unless the said cylinder is in the off position, for preventin short circuiting the entire series resistoriy the said cylinder with the armature shunt established by the said switch mechanism and for requiring that the armature shunt circuit cannot be opened by the said switch mechanism until after the said cylinder is returned to the oil' position.

3. The combination in a system of motor control, of a variable resistor in series with the armature of the motor, a cylinder having an off and a plurality of operative POSI- tions for connecting the motor to a source of suppl and for varying the said resistor, a secon variable resistor, a second separately operable cylinder having an oil position and a plurality of operative positions for connecting the said second resistor in a shunt to the motor armature and for varying the said second resistor, and pivotally cylinder until after the first cylinder has mounted locking members cooperating wit 1 been returned to the of ition.

the said cylinders for preventing the con- In witness whereof, we ve hereunto set nection of the said second resistor in shunt our hands this fourteenth day of February, 15 to the motor armature unless the said first 1923.

c linder is in the off position for preventing short circuitin entirely the said series resistor by the rst cylinder with the armature shunt established by the second cylinder Witnesses: and for requiring that the armature shunt N. EDGEBAN-WAL'ION, circuit cannot be opened by the second J. A. Foam. 

